US1922184A - Soundproof base for machines - Google Patents

Description

Aug. 15, 1933. K; v; WHITE SOUNDPROOF BASE FOR MACHINES Filed Oct. 3, 1931 2 Shets-Sheet 2 F Cas rvf) 5 C W5 W/TNESSfS, INVENTOR 50. A ennefh M Wh/f'e.

Patented Aug. 15, 1933 1,922,1 s4 SOUNDPROOF BASE FQR MACHINES Kenneth M.

White, Lombard, Ill., assignor to Westinghouse Electric 1% Manufacturing Company, a Corporation 5 3 Claims.

specifically, to soundproof non-tilting bases for elevator machines.

Annoyance is frequently caused by noises produced by vibrations set up by machines, such as geared elevator hoist machines, motor-generator sets, ventilating equipment, etc particularly when-mounted on the upper floor of a building. Such noises are of two types: viz. by vibrations transmitted through the air, and

. those caused by vibrations transmitted through the building to more or less remote points.

Noises of the first type may be muffled by enclosing the machine in suitable insulating material to prevent the direct transmission of the vibrations through the air, and noises of the second type may be reduced by interposing a flexible mounting between the machine and the building structure. The latter may be accomplished by merely mounting the machine on some yieldable acoustically-insulating material, such as cork or rubber, or by supporting it on steel springs.

However, when an elevator machine ismounted upon a yieldable base, the external torque applied to the machine by the hoist cables causes it to pitch violently about the axis of the sheave and pulls it out of alignment. The reaction of the motor armature on its frame also causes a pitch in that directio It is, accordingly, an object of my invention to provide a sound-reducing base for elevator machines, and the like, which will maintain the proper alignment thereof with respect to associated apparatus.

It is a further object of vide a yieldable base for remain parallel with the floor, upon, which it is supported, under varyingconditions of service.

Another object of my invention is to provide a sound-reducing base for insulating elevator hoist machines from the building structure.

In accordance with my invention, I support the machine base upon a compressible spring through a system of levers which reduces the weight on the spring. The spring constitutes a yieldable support which absorbs the vibrations transmitted from the machine through the levers.

my invention to pro- The invention itself, however, both as to its of Pennsyl Application October 3, 1931. Serial those caused apparatus which. will vania My invention relates to soundproof bases for machines, and, more organization and its method of operation, togetherv with additional objectsand advantages thereof, will best be understood from the following description, of specific embodiments when read in conjunction with the accompanying drawings, in which:

Figure 1 is a view, in side elevation, of a geared elevator-hoist machine mounted on a sound-reducing base in accordance with my invention;

Fig. 2 is a view, in side elevation, of a soundreducing base comprising a modified embodiment of my invention; j

Fig. 3 is a sectional view taken along line III III of Fig. 2;

Fig. 4 is a view, in side elevation, of a geared elevator-hoist machine mounted on a soundproof base in accordance with a further modificationof my invention; and

Fig. 5 is a diagrammatic sketch demonstrat ing the arrangement and operation of another 7 modification of my invention.

Referring more specifically to the drawings, the apparatus shown in Fig. 1 comprises an elevator car C which is supported by a hoist cable down the hatchway to a counterweight Cwt. The elevator car C is raised and lowered by a geared elevator-hoist machine 13 mounted on a base plate 15.

In order to eliminate the noises and=vibrations which wouldbe transmitted to the building strucary fulcrums 27, floor.

The underside of the machine base 15 is provided with three downwardly extending projections or fulcrums vers 21, 22 and 23 at intermediate points there- The entire weight 01" the elevator hoist machine is supported by the i'ulcrumed levers 21, 22

the base plate, the ratio of the weight supported by the spring may be divided as desired.

My invention is best understood, however, when considered with reference to an assumed operation thereof. 7

In operation, the vibrations set up within the machine are transmitted through the base plate 15 to the levers, which are thereby caused to vibrate on the spring 25. The single spring 25 thereby acts to damp out or absorb the vibrations and prevent their transmission to the building structure. The spring 25 may be comparatively light because of the leverage ratio. It' is to be understood that any suitable energy-absorbing device, such as a dash-pot, may be substituted for, or used with, the spring if desired. The system may be built into the machine base or into a separate base to suit the requirements of the particular installation.

It is important to so design the system of fulcrumed levers that the natural frequency of vibration of the system will be quite different from the frequency of the vibrations to be absorbed. If the system should have a natural frequency which is the same as that of the vibrations to be absorbed, it would. be an efiicient transmitter of such vibrations directly to the building structure. The system is preferably so designed that its natural frequency is lower than that 01; the vibrations to be absorbed. This is readily accomplished by selecting a spring of suitable strength in-accordance with the rule that "few (1,, where f equals the natural frequency of the system;

dst equals the static deflection of the base on its spring, and

9 equals the acceleration caused by gravity.

The vibrating force transmitted to the building structure through a spring mounting can be shown to be proportional to the factor where f, is the natural frequency of the base on its springs and h the frequency of the vibration. (Timoshenko, Vibration problems in engineering) By designing the vibrating system so that its natural frequency is much'lower than the frequencies of vibrations generated by the machine, the coupling of the machine with the building structure is reduced to a minimum at those frequencies, and practically no energy is transmitted thereto.

Although the system of fulcrumed levers permits the machine to move vertically, it always supports its base 15 in a plane parallel to the floor. Assuming that the elevator machine 13 is starting to lift the car C, the reaction of the fulcrum at the end of the base plate adjacent to the hoist sheave will be increased, thereby depressing the 7 spring 25 and lowering the machine. As the levers under the fulcrums 31 and 32 are rotated in a clockwise direction to depress the spring 25, the

lever under the other fulcrum, at the end of the base plate adjacent to the motor, will be rotated in a counter-clockwise direction and will lower the associated end of the base plate 15 arr equal amount. Hence, the base plate 15 moves vertically but remains parallel to the floor at all times, and the machine is not thrown out of alignment.

In Fig. 2, I have shown a modification of my invention, wherein the fulcrums 31, 32 and 33, which depend from the base plate 15, are arranged to engage the levers 21, 22 and 23 near their outer extremities, and the stationary fulcrums 2'7, 28 and 29 engage intermediate portions thereof. The adjacent ends of the levers are pivotally united, as in the first embodiment, but their pivotal joint 24 reacts toward the base-plate 15 rather than toward the fioor because the positions of the fulcrums are relatively reversed. In this modification, the spring 25 or other energyabsorbing device is positioned between the pivotal joint 24 and the base-plate 15. The mode of operation, however, is similar to that previously set forth with reference to the first embodiment.

Although I have shown the levers engaging bearing points 2'7 to 33 as fulcrums, it is to be understood that any other suitable, bearings,

such as antifriction pivotal bearings, may be-provided, if desired.

In Fig. 4 I have illustrated such a modification wherein the base is supported, at one end, on pivotal bearings 41 and. at the other end, on links :42. Such an arrangement has greater flexibility and operates more efficiently to isolate the noises and vibrations.

In either of the modifications disclosed, it is possible to provide a strong coil spring under each of the'supported points of the base to support practically the entire load and thereby reduce the friction on the levers. The set of pivoted levers will then be relieved of the load and will function only to maintain the base parallel with the floor.

I have also found that, by taking into considerationthe inertia of the levers, it is possible to so proportion the apparatus that the transmitted vibrating force will be equal to zero at one particular frequency. For the proof, consider only one lever of an assembly supporting its share of the load, as shown in Fig. 5. i

The static load supported at point A by the building structure may be disregarded, since it is constant. Assume a periodic disturbing force applied at B which has a magnitude, at any time t,

of P cos wt. Then the displacement of the base at any time, i, will be M cos wt, where M is the maximum amplitude of the vibration. The change in length of the spring at C will then be (M cos wt) (1+2) The spring force built up by this change will be (M cos wt) (1+2) k,

where k is the spring constant, or load required to produce unit change in length.

The force transmitted to point B by the lever will be b b (M cos wt) (1+ ;)k;- I

The force on point A due to the spring is the sum of the forces at points B and C, and is (M cos wt) (1+ g) k.

As a result ofthe movement of the lever about point A, an inertia force is produced. The angle of rotation, 0, at any instant is 1 (M cos wt) Velocity of rotation,

::= (sin wt) Torsional acceleration,

21 I;!: (cos wt) The torque due to this acceleration is m is g d! where is the moment of inertia of mass of the lever about A.

The force at A due to this torque is:

I. d o I W -;'g t T82 (M COS Wt) Therefore the total vibrating force at A,

.I,, But w=21rf, where f=freq. of disturbing force.

Therefore r [2 4I' I 1 8 v of my invention to rearrange the levers or to provide additional levers to support the machine at as many different points as desired.

It will be seen that I have provided a soundreducing base for machines which yields to absorb the vibrations of the machine, and stresses on the machine, but which maintains the proper alignment thereof with respect to associated apparatus.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except as necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In combination, a machine-supporting base, a three-point vibration-absorbing support ,therefor comprising three levers having adjacent ends pivotally united in Y formation, bearings projecting downwardly from the base to engage intermediate portions of the levers, bearings projecting upwardly from the floor for engaging the free extremities of the levers, and yieldable vibration-absorbing means between the pivotal joint of the levers and the floor.

2. In combination, a machine-supporting base, a single vibration-absorbing means, and a system of levers for supporting the base at a plurality of points and cooperating with said vibration-absorbing means to apply a portion of the weight from each point to the vibration-absorbing means.

3. In combination, a machine-supporting base, a three-point vibration-absorbing support therefor comprising three levers having adjacent ends pivotally united in Y formation, bearings projecting downwardly from the base for engaging the free extremities of the levers, bearings projecting upwardly from the floor for engaging intermediate portions of the levers, and yieldable vibration-absorbing means interposed between the pivotal junction of the levers and the base.

KENNETH M, WHITE.

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